Ha! (L.o.l.) That's what most people ask or they think it's a motorcycle battery. It's a legit 11lb. 360 cca car battery made by Braille in Florida.
They make a bunch of really interesting and ultra lightweight batteries mostly for race cars, sports cars, and some other applications.

In reply to # 1477458 by barry s
Aaron - Is that a lawn mower battery?

I would recommend that you check the output of the alternator before assuming that the battery has died.

I use an Interstate MT-7 AGM battery (MT7-34), 800 CCA, CA 1000 in my TR6. I've had very good luck with Interstate batteries. I have two U.S. Army deuces, M35A2 and M35A3 that use two 6TL batteries for 24 volts. I just replaced the Interstate 6TLs in one truck that had date codes over ten years ago. The Interstate 6TLs in the other truck failed after 9 years. I always have battery minders hooked up to my vehicle batteries unless the vehicle is driven daily. Good quality battery minders will definitely extend the life of your batteries.

As we have seen in this thread, there are a number of different types of batteries including lithium batteries (like Aaron's, I assume) that are much smaller and lighter than traditional types. They are somewhat more expensive and require a special type of charger but hold a charge longer. I have one in my motorcycle where the weight savings is a factor. It came with a selection of foam blocks to hold it place in the battery box.

My preference for my TR, however, is a traditional looking battery that fills out the battery tray and hold-down hardware..

In reply to # 1477433 by Tote
100% agree! In 1969 battery technology was such that you needed a large battery to turn over the high load Lucas starter. But in 2017 and gear reduction starters, a battery of original size today is probably overkill, a simple lawn tractor battery could probably get the job done. I use a much smaller AC Delco side terminal unit from a Cavalier to run the TR6...it works a charm and I can use it in my other cars. Weight reduction is the best horsepower gain...I know, starting with the driver...me bad.

As the OTHER Tony M suggests,
I have used U1 lawnmower batteries for the last 10 years. Last year I bought my 2nd NEW battery (the first one I used came out of a junk lawnmower and only lasted 2 years!)

In the spring Walmart will have them on sale, last year I paid only $25can.

Never had a problem starting (with a GR starter) but then I seldom use the car when the weather is close to freezing.

During winter storage, the battery is hooked to a 2amp charger that is plugged into a 'Chrismas light' timer.
It charges for 1/2 hour a day.

The next two pics should have everyone recoiling in horror of what I did with my battery. I used a bulkhead connection, 1Ga welding cable and custom brackets from a hardware store. I don't carry a spare but two cans of puncture seal and a tool kit in there.

Why? Well back in the day (1990's), I was trying out new ideas and weight distribution was one of them. I figure I could lower and move back all that weight by relocating and spare the battery engine heat. The engine battery tray makes a great tool shelf when working on things and I have the fuel line off the engine routed over the battery tray area. Also, I can disconnect and lock the trunk in an attempt to foil thieves.

In reply to # 1477784 by Tote
The next two pics should have everyone recoiling in horror of what I did with my battery. I used a bulkhead connection, 1Ga welding cable and custom brackets from a hardware store. I don't carry a spare but two cans of puncture seal and a tool kit in there.

Why? Well back in the day (1990's), I was trying out new ideas and weight distribution was one of them. I figure I could lower and move back all that weight by relocating and spare the battery engine heat. The engine battery tray makes a great tool shelf when working on things and I have the fuel line off the engine routed over the battery tray area. Also, I can disconnect and lock the trunk in an attempt to foil thieves.

I had a 2013 Dodge RAM 1500 5.7 Hemi. I came out from shopping at Wal-Mart and got in and turned the key. The dash lights and warning lights came on as always but then everything went black. I popped the hood and saw that the battery cables were in the process of melting the insulation from the wires. I didn't have any tools so all I could do was watch as the melting wiring spread to every other wire that I could see.
I went in and told the manager at Wal-Mart and they called the fire dept.
By the time I got back outside the truck was engulfed in flames. It burned to a crisp right there in the Wally World parking lot. Of course it was totalled but I was told that the battery shorted internally and sent power backwards through the entire system. I really don't think it's possible to reverse polarity but something definitely shorted and the insurance company claimed it was the battery.